Appendix 4: Phytolith Analysis of Sites LU-69 and PU-165

Abstract

A total of 20 samples from sites LU-69 and PU-165 were processed, identified, and counted at the University of Exeter Archaeobotany Laboratory. Phytolith extractions from the archaeological sediments followed standard procedures. Samples were deflocculated in a shaker with Calgon for 24 h. Clays were washed by gravitational sedimentation, carbonates were removed using hydrochloric acid, and organic matter was removed with nitric acid and potassium chlorate when necessary. Samples were floated in a zinc bromide solution at a specific density of 2.3 g/ml, dried in acetone, and mounted in Permount. In order to maximize the recovery of important phytoliths of different size classes, such as those that derive from the rinds of Cucurbita fruits and leaves and cobs of maize, archaeological sediments were separated by wet sieving into silt (2–50 µm) and sand (50–2,000 µm) fractions. The entire extract recovered from the sand fraction was scanned in search for Cucurbita phytoliths and other large arboreal and economic plant forms. Extended counts of the silt fraction were carried out in order to obtain a large sample of cross-shaped phytoliths in order to detect the presence of maize leaf phytoliths. Only sample No. 28 from PU-165 did not contain crosses, which prevented carrying out the discriminant function to test the presence of a maize leaf phytolith.